The present invention relates to an X-ray shadow graph device for observing the dynamic change of a sample excited by light or voltage pulses by exposing the sample to a precisely controlled X-ray pulse with an extremely short duration of time.
FIG. 1 shows a cross-sectional view of the conventional X-ray shadow graph device.
An X-ray tube 20 used in the conventional X-ray shadow graph device consists of a heater 18, cathode 17 to emit electrons, control grid 16 and electron lens 15. A target 14 to generate X rays is accomodated in a vacuum envelope 19 having a window 13 consisting of beryllium (Be). A control pulse is applied to control grid 16 of X-ray tube 20, a pulse current is emitted from cathode 17, and an X-ray pulse 8 having a short duration time is generated by striking the target with the pulse current.
The transmission image or transmission diffraction image is recorded on image recording device 10 when sample 9 is exposed to the X-ray pulse 8 having an extremely short duration time.
In the conventional X-ray tube, a pulse voltage is applied to the control grid thereof in order to generate the electron pulse required for generating the X-ray pulse. Due to the capacitance of the electrodes, the minimal pulse width available in the conventional X-ray tube is limited to 1 ns or longer.
The objective of the present invention is to present an X-ray shadow graph device wherein a new type of X-ray pulse tube is used to generate X rays responding to an electron beam emitted from the X-ray pulse source forming a photocathode which is formed in the X-ray tube and is excited with extremely short light pulses generated by a laser device.